NiCoSx@cobalt carbonate hydroxide obtained by surface sulfurization for efficient and stable hydrogen evolution at large current densities

Developing earth-abundant, active, and stable electrocatalysts for hydrogen evolution reactions (HERs) at large current densities has remained challenging. Herein, heterostructured nickel foam-supported cobalt carbonate hydroxide nanoarrays embellished with NiCoSx nanoflakes (NiCoSx@CoCH NAs/NF) are designed via room-temperature sulfurization, which can drive 10 and 1000 mA cm-2 at low overpotentials of 55 and 438 mV for HER and exhibit impressive long-term stability at the industrial-level current density. Surprisingly, NiCoSx@CoCH NAs/NF after a 500 h stability test at 500 mA cm-2 exhibit better catalytic performance than the initial one at high current densities. Simulations showed that NiCoSx@CoCH NAs have an optimized hydrogen adsorption free energy (ΔGH*) of 0.02 eV, owing to the synergistic effect of CoCH (ΔGH* = 1.36 eV) and NiCoSx (ΔGH* = 0.03 eV). The electric field at the heterostructure interface leads to electron transport from CoCH to NiCoSx, which enhances HER dynamics. The hierarchical nanostructure has a large specific area and a superaerophobic surface, which are beneficial to hydrogen generation/release for efficient and stable HER.